| 摘要 |
PURPOSE:To discriminate the presence of a call until the next call is received, through the illumination of a lamp, by displaying the incoming call with a squelch signal through the illumination of lamp and keeping the display until a press-to-talk switch is operated. CONSTITUTION:A signal converted into an intermediate frequency is converted into a sound at a speaker 5 via an amplitude limiter 1, a discriminator 2, a switching circuit 3, and an audio amplifier 4. A noise signal detected at a band pass filter 6 is converted into a DC signal (a) at a detector 8 through an amplifier 7, and a squelch signal (c) is discriminated with a threshold level (b) of a level discriminating circuit consisting of a variable resistor 9 and a Schmitt circuit 10. The squelch signal (c) turns on the switching circuit 3 and is given to a holding circuit 12, which illuminates a lamp of a display circuit 11 with the squelch signal (c) and holds the illuminating state (e) until a press-to-talk signal (d) is inputted. |
